Thank you for the link to the "Embed Comic Metadata" plugin. I think this is the closed I will get to what I want. I managed to embed the data,checked this by opening the CBZ file with WinRar. Comments are in the file

. Great, next step:
I tried to use CC for library management and downloading, but CC has no CBR support. The download button is not activated when the document is CBR. That is why I tested FBReader. Download will work there.
However, please note that both FBReader and CC show the correct bookname and series when browsing the library to this point. Since CC does not support CBR/CBZ downloads, I did the download in FBReader. When looking at the book description/book info, it still was missing the correct info in FBReader.
So next I opened the CBR in ComicRack on Android. Here the manually entered meta tags and comments are visible. The comments are not using any html tags though, but it is better then nothing.
This leaves me with one challenge: ComicRack does not offer download from the Calibre network library. Or am I wrong? Because if so, I need to use FBReader for downloading CBZ, and ComicRack for reading.
Could this go any simpler ??